Shape of a Light

Assigning a shape to a light modifies the illumination of a scene.

Just as a light can have a color, it can also be assigned a shape. For example, a rectangular shape acts like panel lighting in a ceiling. A linear shaped light acts like a narrow fluorescent tube.

Note: The shape of a light is supported for backwards compatibility with AutoCAD 2015-based products and earlier releases.

The shape of a light can be set as it is being added to a scene or after it has been placed. The follow provides an overview of setting the shape of a:

• New light. Use the Shape option after enabling Soft (sampled) shadows from the Shadow option of the LIGHT command, or one of the commands used to add a specific type of light.
• Existing light. Use the Shape property after setting the Type property (under the Render Shadow Details panel) to Soft (sampled).

Shapes available for selection depend on the type of the light:

• Spotlight: Rectangular and Disk
• Point light and Weblight: Linear, Rectangular, Disk, Cylinder, and Sphere

SPOTLIGHT (Command)

Creates a spotlight that emits a directional cone of light.

 Find

A spotlight distribution casts a focused beam of light like a flashlight, a follow spot in a theater, or a headlight.

Note: Starting with AutoCAD 2016-based products, all standard lights are calculated as photometric lights. It is recommended to update all standard lights in a scene to photometric lights. Photometric lighting is enabled by setting the LIGHTINGUNITS system variable to 1 or 2.

The following prompts are displayed.

Note: The options for this command vary slightly depending on the LIGHTINGUNITS setting.

Source location

Sets the location for the spotlight. Enter coordinate values or click a location in the drawing area.

Source location

Sets the spotlight target. Enter coordinate values or click a location in the drawing area.

Name

Specifies the name of the light. You can use uppercase and lowercase letters, numbers, spaces, hyphens (-), and underscores (_) in the name.

Intensity/Intensity factor

Sets the intensity or brightness of the light. The range is 0.00 to the maximum value that is supported by your system.

Hotspot

Specifies the angle that defines the brightest cone of light, which is known to lighting designers as the beam angle. This value can range from 0 to 160 degrees or the equivalent values based on AUNITS.

Falloff

Specifies the angle that defines the full cone of light, which is also known as the field angle. This value can range from 0 to 160 degrees. The default is 50 degrees or the equivalent values based on AUNITS. The falloff angle must be greater than or equal to the hotspot angle.

Status

Turns the light on and off.

Photometry

Photometry is the measurement of the luminous intensities of visible light sources.

In photometry, luminous intensity is a measure of the perceived power emitted by a light source in a particular direction. Luminous flux is the perceived power per unit of solid angle. The total luminous flux for a lamp is the perceived power emitted in all directions. Luminance is the total luminous flux incident on a surface, per unit area.

Note: The Photometry option is available only when the LIGHTINGUNITS system variable is set to 1 or 2.

Intensity

Enter an intensity value in candelas, flux value, or illuminance value.

• Intensity. Sets intensity based on candelas (cd), the SI base unit of luminous intensity. This value sets the perceived power emitted by a light source in a particular direction.
• Flux. Sets intensity based on lux (lx), an SI unit of illuminance.
• Illuminance.Sets intensity based on foot-candles (fc), the American unit of illuminance. Specify a distance to use to calculate illuminance.

Color

Specifies the color of the light.

• Color name. Specifies the name of the light color.
• ?. Displays a list of color names.
• Kelvin. Specifies the color based on a Kelvin temperature value.

Exit

Exits the Photometry prompt.

Shadow

Makes the light cast shadows.

Note: Starting with AutoCAD 2016-based products, shadows are always rendered no matter the current status or values of the Shadow option. This option is maintained for scripting and backwards compatibility.

Off

Turns off display and calculation of shadows for the light. Turning shadows off increases performance.

Sharp

Displays shadows with sharp edges. Use this option to increase performance.

Soft Mapped

Displays realistic shadows with soft edges.

• Map Size. Specifies the amount of memory to use to calculate the shadow map.
• Softness. Specifies the softness to use to calculate the shadow map.

Soft Sampled

Displays realistic shadows with softer shadows (penumbra) based on extended light sources.

• Shape. Species the shape of the shadow (disk or rectangle) and its dimensions (radius or shape and width).
• Samples. Specifies the size of the sample.
• Visible. Specifies whether the shape of the shadow is visible.
• Exit. Returns to the previous prompt.

Attenuation

Controls how light diminishes over distance. The farther away an object is from a spotlight, the darker the object appears. Attenuation is also known as decay.

Note: When the LIGHTINGUNITS system variable is set to 1 or 2, the Attenuation option has no affect on the light when rendered. This option is maintained for scripting and backwards compatibility.

Attenuation Type

Sets whether and how attenuation is displayed. The farther away an object is from a point light, the darker the object appears. Attenuation is also known as decay.

• None. Sets no attenuation. Objects far from the spotlight are as bright as objects close to the light.
• Inverse Linear. Sets attenuation to be the inverse of the linear distance from the light. For example, at a distance of 2 units, light is half as strong as at the spotlight; at a distance of 4 units, light is one quarter as strong. The default value for inverse linear is half the maximum intensity.
• Inverse Squared. Sets attenuation to be the inverse of the square of the distance from the light. For example, at a distance of 2 units, light is one quarter as strong as at the spotlight; at a distance of 4 units, light is one sixteenth as strong.

Use Limits

Specifies whether to use limits.

Attenuation Start Limit

Specifies the point where light starts as an offset from the center of the light. The default is 0.

Attenuation End Limit

Specifies the point where light ends as an offset from the center of the light. No light is cast beyond this point. Setting an end limit increases performance where the effect of lighting is so minimal that the calculations are wasted processing time.

Color/Filter Color

Controls the color of the light.

True Color

Specifies a True Color. Enter in the format R,G,B (red, green, blue).

Index

Specifies an ACI (AutoCAD Color Index) color.

HSL

Specifies an HSL (hue, saturation, luminance) color.

Color Book

Specifies a color from a color book.

Exit

Exits the command.

Creating a Point Light in Photometric Workflow

1. Click Visualize tab  Lights panel (expanded)  Lighting Units drop-down  American Lighting Units  Find or International Lighting Units  Find.
   Photometric lighting is enabled, and American or International lighting units is set.
2. Click Visualize tab  Lights panel  Create Light drop-down  Point.  Find
3. Specify a location for the light.
4. At the Command prompt, enter n and enter a name.
   This name appears in the Properties and Lights in Model palettes.
   You can continue to specify properties by entering options, or you can exit and set properties interactively. When you use the interactive method, you can see the results of your changes as you work.
5. Press Enter to exit the command.
   Select the light and use grip editing to modify the light. You can also right-click the light and then click Properties to modify the properties of the light in the Properties palette.

Point Lights

A normal point light does not target an object, but illuminates everything around it. Point lights can be used for general lighting effects and simulate lighting sources such as candles and light bulbs.

A target point light has additional target properties so it can be directed to an object. It can also be created from a point light by changing the Targeted property of the point light from No to Yes.

In the standard lighting workflow, you can set a point light manually so its intensity diminishes with respect to distance either linearly, according to the inverse square of the distance, or not at all. By default, the attenuation is set to None.

Note: Starting with AutoCAD 2016-based products, all standard lights are calculated as photometric lights. It is recommended to update all standard lights in a scene to photometric lights.

Point Lights in Photometric Workflow

A point light can have photometric distribution properties. The attenuation for a photometric point light is always set to inverse square.

When the LIGHTINGUNITS system variable is set to 1 (American units) or 2 (International SI units) for photometric lighting, additional properties are available for a point light. The following photometric properties can be set via the Properties palette:

• Lamp Intensity. Specifies the inherent brightness of the light. Specifies the intensity, flux or illuminance of the lamp.
• Resulting Intensity. Gives the final brightness of the light. (Product of lamp intensity and intensity factor. Read-only.)
• Lamp Color. Specifies the inherent color of the light in Kelvin temperature or standard.
• Resulting Color. Gives the final color of the light. This is determined by a combination of the filter and lamp colors. (Product of filter and lamp color. Read-only.)

When the drawing lighting units are photometric, the attenuation type property becomes disabled. Photometric lights have fixed, inverse-square attenuation.

The following image is an example of a photometric point light with the photometric properties outlined on the Properties palette:

Note: In the legacy standard lighting workflow, you can set a point light manually so its intensity diminishes with respect to distance either linearly, according to the inverse square of the distance, or not at all. By default, the attenuation is set to None.

Creating Sunlight - DISTANTLIGHT command

Creates a distant light.

 Find

Note: Starting with AutoCAD 2016-based products, all standard lights are calculated as photometric lights. It is recommended to update all standard lights in a scene to photometric lights. Photometric lighting is enabled by setting the LIGHTINGUNITS system variable to 1 or 2.

The following prompts are displayed.

Note: The options for this command vary slightly depending on the LIGHTINGUNITS setting.

Light Direction

Specifies the direction of the distant light with two points, a point to start from and a second point to go toward. The Vector option provides a method to specify the coordinates that represent the vector direction of the light. For example, the default value of the vector coordinates 0.0000,-0.0100,1.0000, points the light approximately in the positive Z-axis direction.

Name

Specifies the name of the light. You can use uppercase and lowercase letters, numbers, spaces, hyphens (-), and underscores (_) in the name. The maximum length is 256 characters.

Intensity/Intensity Factor

Sets the intensity or brightness of the light. The range is 0.00 to the maximum value that is supported by your system.

Status

Turns the light on and off. If lighting is not enabled in the drawing, this setting has no effect.

Photometry

Photometry is the measurement of the luminous intensities of visible light sources.

In photometry, luminous intensity is a measure of the perceived power emitted by a light source in a particular direction. Luminous flux is the perceived power per unit of solid angle. The total luminous flux is the perceived power emitted in all directions. Luminance is the total luminous flux incident on a surface, per unit area.

Note: The Photometry option is available only when the LIGHTINGUNITS system variable is set to 1 or 2.

Intensity

Enter an intensity value in candelas, the perceived power in a luminous flux value, or illuminance value for the total luminous flux incident on a surface.

• Candela (symbol: cd) is the SI unit of luminous intensity (perceived power emitted by a light source in a particular direction). Cd/Sr
• Lux (symbol: lx) is the SI unit of illuminance. Lm/m^2
• Foot-candle (symbol: fc) is the American unit of illuminance. Lm/ft^2

Enter f to specify the perceived power in a luminous flux value.

If you enter i, you can specify the intensity of the light based on an illuminance value.

The illuminance value can be specified in either lux or foot-candles. Enter d to specify a distance to use to calculate illuminance.

Color

Specify the color of the light based on a color name or a Kelvin temperature. Enter ? to display a list of color names.

Enter a text string using wild card characters to display a partial listing of color names, or an asterick (*) to display all the possible choices.

If you enter k, you can specify the color of the light based on a Kelvin temperature value.

Shadow

Makes the light cast shadows.

Note: Starting with AutoCAD 2016-based products, shadows are always rendered no matter the current status or values of the Shadow option. This option is maintained for scripting and backwards compatibility.

Off

Turns off the display and calculation of shadows for the light. Turning shadows off increases performance.

Sharp

Displays shadows with sharp edges. Use this option to increase performance.

Soft Mapped

Displays realistic shadows with soft edges.

Specifies the amount of memory that should be used to calculate the shadow map.

Specifies the softness to use to calculate the shadow map.

Color/Filter Color

Controls the color of the light.

True Color

Specifies a True Color. Enter in the format R,G,B (red, green, blue).

Index

Specifies an ACI (AutoCAD Color Index) color.

HSL

Specifies an HSL (hue, saturation, luminance) color.

Color Book

Specifies a color from a color book.

Setting Geographic Location from a GIS File

You can insert geographic location information to a drawing file by importing the coordinates of a position mark from a *.kmz or *.kml file.

1. Click Insert tabLocation panelSet Location drop-downFrom File.  Find
2. In the Set Location from File dialog box, select the file to import the location from.
3. Click Open.
   The Geographic Location dialog box displays. The Latitude and Longitude boxes show the extracted location. If the file contains multiple position marks, only the first is extracted.
   Note: If the Geolocation - Online Map Data task dialog box displays, close it by clicking any button.
4. Click Next.
5. In the GIS Coordinate System list, select a coordinate system.
   Tip: The coordinate system that has its datum closest to the marker location provides the best results. By default, this is the first coordinate system in the list.
6. Click Continue.
7. In the drawing area, click the position that corresponds to the location you specified.
8. At the command prompt, enter the angle from the X axis to the north direction.

Setting Geographic Location from a Map - AutoCad Civil 3D

You can insert geographic location information to a drawing file by specifying the location of a reference point on a map provided by an online maps service.

Note: You must be signed in to your Autodesk account to use the online maps service.

1. Click Insert tabLocation panelSet Location drop-downFrom Map.  Find
2. If the Geolocation - Online Map Data task dialog box displays, click Yes.
3. In the Geographic Location dialog box, in the Address box, type the name of a landmark or road near the reference location and click .
   Tip: If you know the latitude and longitude of a nearby location, you can search for that as well.
   .
4. In the results pane, on the result nearest to the reference location, click Drop Marker Here.
   A marker is inserted in the map.
   Tip: Instead of searching, you can zoom the map, right-click the location and click Drop Marker Here.
5. Zoom the map such that the marker and the location to set are clearly visible.
6. Drag the geographic marker to the desired location.
   Tip: Instead of dragging the marker, you can right-click the desired location and click Move Marker Here.
7. Click Next.
8. In the GIS Coordinate System list, select a coordinate system.
   Tip: The coordinate system that has its datum closest to the marker location provides the best results. By default, this is the first coordinate system in the list.
9. Click Continue.
10. In the drawing area, click the position corresponding to the location you selected in step 6.
11. At the command prompt, enter the angle from the X axis to the north direction.